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The right roller makes a difference between hair that has the lift and body you crave and hair that falls out of too-loose curls or looks super springy. Big and medium rollers give wave, curl or body to medium-length and long hair. Do a test curl before you commit, so you know what to expect from the roller size.
Curl Finish
The choice between big and medium rollers can affect the curl size. In general, larger rollers give looser curls or waves, medium rollers give body curls and small rollers give tight curls. The more times the hair gets wrapped around the roller, the tighter the resulting curl. Long hair rolled on big rollers and shoulder-length hair rolled on medium rollers can have similar curl finish if the hair gets wrapped an equivalent amount.
Guidelines
Since hair length is a major player in determining the curl finish, use a general guideline to evaluate potential rollers that work for your mane. One revolution around a roller gives loose C-shaped waves. One to two revolutions gives full waves. More than two revolutions give bouncy curls. Test-wrap your hair around a roller before you commit.
Curl Volume
The angle you use to set the rollers controls the volume and lift you'll get. If you set big or medium rollers at a 45-degree angle, the curls will have reduced root lift for less overall volume. If you set either big or medium rollers at a 90-degree angle, the curls will have greater volume and root lift. This gives you the power to create voluminous waves with big rollers or sleek and bouncy curls with medium rollers.
Roller Size and Type
Choose from velcro rollers, sponge rollers, hot rollers, perm rods, magnetic rollers or spiral rods. For all rollers, sizes are clearly marked so you can easily tell the difference. For example, perm rods are color-coded. Medium rollers are pink or gray, and large rollers are white or purple. Medium perm rods give curl to medium-length hair and generally aren't suited for long hair, because they would add too much curl. Large perm rods curl very long hair, wave long hair and give light body to medium-length hair.

